1. Technical Field
The invention relates to a toner supplying apparatus in an electrophotographic system of image forming apparatus, and to an image forming apparatus.
2. Related Art
The image forming apparatus has a problem of a difficulty from a mechanical space point of view in disposing a toner storage for storing a toner in the vicinity of a developing device because of a large volume of the storage.
In order to solve such a problem, a toner supplying technology has been disclosed for transferring the toner from the toner storage to the developing device by using a toner transferring method called an air-transfer that can transfer the toner far.
The toner supplying apparatus using the air-transfer method basically includes a toner storage having a toner mixing chamber, a fluid transferring member for transferring mixed fluid of the toner and air-stream from the toner storage, and a toner separating member for separating the toner from the transferred mixed fluid.
A part of the air-stream separated from the toner is usually returned to the mixing chamber via the fluid transferring member without discharging outside. Sometimes the toner separating member has been provided with a filter for preventing the toner from scattering outside and for releasing only a part of the air-stream outside to adjust the air pressure within a supply path. There has been also disclosed a technology of returning the air-stream in a developing device to a toner supplying apparatus passing through a transferring pipe between the developing device and the toner supplying apparatus, or a technology of returning the air-stream outside through a filter provided on a developing device. Further disclosed is a technology in which a bladed wheel called a rotary valve and a seal are provided between a developing device and a mixed fluid transferring part to avoid toner scattering from the developing device (for example, JP-Tokukaihei-11-242416A).
However, in the method of returning the air-stream in the developing device to the toner supplying apparatus through the transferring pipe connecting between the supplying apparatus and the developing device, if the transferring pipe is long, air-flow resistance inside the transferring pipe increases so that the air-stream within the developing device cannot return to the toner supplying apparatus in a short time, thereby there is a large possibility of scattering the toner from the developing device.
In the method of providing the developing device with a filter to release the air-stream to the outside, the filter needs to be exchanged periodically, which is troublesome, and missing the periodic exchange of filter causes the filter to be clogged to prohibit the air-stream from passing through the filter, thereby scattering the toner from the developing device may cause.
In the method of providing the rotary valve and the seal between the developing device and the fluid transferring part, long-time rotation of the bladed wheel of the rotary valve causes the toner to enter a sliding part between the edges of the blades and the seal with resultant melting and sticking of the toner.